The primary objective of this project is to remove certain ambiguities concerning the reduction of nitrite by ascorbic acid. The specific aims of the project are to determine: 1) if nitrous oxide (N20) and dinitrogen (N2) are formed in significant amounts; 2) what is the pH range where the reaction occurs at a measurable rate; 3) if nitroxyl (HNO, nitrosyl hydride) and/or oxyhyponitrite are formed as intermediates in the reaction above pH 5; and 4) if the kinetics and mechanism of the reaction are different in the pH range 5-7.5 than that observed at lower pH. N-nitrosamines are powerful carcinogens and can be formed whenever a nitrosating agent, such as nitrite, reacts with a secondary or tertiary amine under appropriate conditions. Nitrites are known to readily nitrosate amines in solutions below pH 4 and can nitrosate amines in neutral or basic solution if catalysts such as formaldehyde or chloral are present. Ascorbic acid is routinely added to processed foods containing nitrites to block the formation of nitrosamines. Although the reduction of nitrite by ascorbic acid has been extensively studied, surprising gaps and uncertainties in our understanding of this important reaction remain. Vacuum line techniques will be used to study the gaseous products of the nitrite-ascorbate reaction. Gas chromatography and FT-IR spectroscopy will be used to quantitate the gases produced. 15N- labelled nitrite will be used to determine whether nitroxyl is formed as an intermediate in nitrite reduction at pH values above 5. A kinetics study will be carried out using UV-visible spectroscopy to extend the knowledge about the kinetics and mechanism of this reaction into a range not previously studied.